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\textbf{Introduction}  In order for systematic reviews to make accurate inferences concerning clinical therapy, the primary studies that constitute the review must provide valid results. The Cochrane Handbook for Systematic Reviews states that assessment of validity is an “essential component” of a review that “should influence the analysis, interpretation, and conclusions of the review.” review”(P. 188) (2008)\cite{2008}  The internal validity of a review’s primary studies must be considered to ensure that bias has not compromised the results, leading to inaccurate estimates of summary effect sizes. In ophthalmology, there is a need for closer examination of the validity of primary studies comprising a review. As an illustrative example, Chakrabarti et al (2012) \cite{Chakrabarti_2014}discussed emerging ophthalmic treatments for proliferative (PDR) and nonproliferative diabetic retinopathy (NDR) noting that anti-vascular endothelial growth factor (VEGF) agents consistently received recognition as a possible alternative treatment for diabetic retinopathy. Treatment guidelines from the Scottish Intercollegiate Guidelines Network and the American Academy of Ophthalmology consider anti-VEGF treatment as merely \textit{useful as an adjunct} to laser for treatment of PDR; however, the Malaysian guidelines indicate that these same agents were \textit{to be considered in combination} with intraocular steroids and vitrectomy. Most extensively, the National Health and Medical Research Council guidelines \textit{recommend the addition} of anti-VEGF to laser therapy prior to vitrectomy. The evidence base informing these guidelines is comprised of trials of questionable quality. Eldaly et al. (2014) conducted a systematic review of this anti-VEGF treatment for diabetic retinopathy, which included 18 randomized controlled trials (RCTs). Of these trials, seven were at high risk of bias while the rest were unclear in one or more domains. The authors concluded, “there is very low or low quality evidence from RCTs for the efficacy and safety of anti-VEGF agents when used to treat PDR over and above current standard treatments". Thus, low quality evidence provides less confidence regarding the efficacy of treatment, makes suspect guidelines advocating use, and impairs the clinicians ablility to make sound judgements regarding treatment.  
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